. >>> and later, treasures from camelot. jfk, jackie kennedy, the incredible collection hidden away until now. >>> back now with as we mentioned that warning about your computer and the frighteningly easy way strangers have figured out now to gain access to your home and watch, in effect, every move you make. all it takes is one bad incoming e-mail, and the camera on your computer turns on, and then someone is spying on you, without you knowing it. we get our report on this tonight from nbc's jeff rossen. >> reporter: these teenagers don't know it, but a stranger is spying on them. inside their bedroom. >> what about you? >> reporter: and in their dining room, as the family eats dinner. little do they know, thousands of miles away, this man has broken into their laptop, and turned on their web cam. >> people who are victims generally have no idea they are victims. >> reporter: that man is working with us, computer expert, jim stickley. he says families like this are easy targets for web cam predators. like luis mijangos. prosecutors say he was spying on over 200 women through their web cams.